Blends of cellulose triacetate with methyl acrylate polymer



United States Patent 3,277,032 BLENDS 0F CELLULOSE TRIACETATE WITHMETHYL ACRYLATE POLYMER John R. Caldwell, Kingsport, Tenn., assignor toEastman Kodak Company, Rochester, N.Y., a corporation of New Jersey NoDrawing. Original application Nov. 3, 1958, Ser. No. 771,187, now PatentNo. 3,026,276, dated Mar. 20, 1962. Divided and this application Jan. 4,1962, Ser.

3 Claims.

This is a divisional application of US. patent appli cation Serial No.771,187, filed November 3, 1958, now issued at Patent No. 3,026,276 onMarch 20, 1962.

This invention concerns a modification of cellulose triacetate withvinyl polymers in order to improve the cellulose triacetate fibers.

Cellulose triacetate is a well-known composition which may be used forpreparing fibers for use in fabrics, and for sheeting which may be usedfor such purposes as photographic film base. However, it is desirable tomodify the cellulose triacetate in order to improve certain of thecharacteristics of the material which are inherent in cellulosetriacetate itself. For instance the cellulose triacetate is relativelyinsoluble in such solvents as acetone and the like which can normally beused with cellulose acetate. Moreover, cellulose triacetate is arelatively hard film material which must be plasticized in order toenable it to be used for various purposes such as film base, fibers, andthe like. However, in order to plasticize this material, it has beendesirous to find some means which would plasticize the material withoutexuding, evaporating or the like, with the result that the materialbecomes brittle.

I have found a method of modifying cellulose triacetate with vinylpolymers which provides improved solubility of the triacetate in suchsolvents as acetone and which also plasticizes the cellulose triacetateso that the plasticizer becomes an integral part of the finalcomposition and will not wash out or exude, and which is inert tophotographic emulsion.

One object of this invention is to provide a plasticized cellulosetriacetate. Another object of the invention is to provide clear, stablesolutions or dopes of cellulose triacetate and a vinyl polymer in anon-solvent for cellulose triacetate. A further object is to providefibers and films of cellulose triacetate which can be dyed with thecommon types of dye by standard methods. A further object is to providenew cellulose triacetate compositions that are soluble in acetone. Anadditional object of the invention is to provide acetone solutions withcellulose triacetate. A further object of the invention is to provide amethod for dissolving cellulose triacetate in acetone. Another object isto provide a method for manufacturing films and fibers of cellulosetriacetate from acetone solutions. Still another object is to providecellulose triacetate compositions that are soluble in esters, alcohols,and higher ketones.

To carry out my invention, I form a vinyl polymer in the presence ofdissolved or swollen cellulose triacetate. Cellulose triacetate may betreated with a liquid which acts as a swelling or softening agent but isa non-solvent. The materials which may be used in my invention includewater, acetic acid, and the like. The resulting blend can be converteddirectly to fibers or films by extrusion into a suitable precipitatingbath. Thus a vinyl polymer may be formed in a solution of cellulosetriacetate in a solvent other than acetic acid, such asdimethylsulfolane, ethylene chlorohydrin, methylene chloride, amethylene chloridemethanol mixture containing at least 50% methylenechloride and the like. The resulting solution can be used 3,277,032Patented Oct. 4, 1966 "ice directly or may be treated with aprecipitating agent to isolate the blend'l In another embodiment aceticacid may be used as a solvent for cellulose triacetate and anacetone-soluble vinyl resin blended with the cellulose triacetate inacetic acid solution. The blend is then precipitated to form an intimatemixture of the vinyl resin and cellulose triacetate. These precipitatedmixtures will dissolve or disperse in acetone even when they contain ashigh as triacetate. The acetone solutions can be spun by the usualdryspinning methods to give fibers; they can be coated or cast to giveclear, flexible films. Therefore, the modified cellulose triacetate maybe used in conventional cellulose acetate equipment without changing thedesign appreciably.

When plasticizing the cellulose triacetate according to my invention,the vinyl material is incorporated as a monomer which is absorbed eitherin a solution of cellulose triacetate or in the swollen cellulosetriacetate depending upon whether a solvent or non-solvent is employed.The vinyl monomer or mixture of vinyl monomers are polymerized afterthey have been added to the cellulose triacetate along with a catalyst,and allowed to penetrate into the gel structure of the triacetate.

In a preferred embodiment of my invention, cellulose triacetate isjelled or swollen using water. This form of triacetate structure isobtained by precipitating an acetic acid dope of triacetate in water.The precipitate is washed but not dried. In this form, particles ofprecipitate consist of a gel that contains a relatively large proportionof water. Monomers can diffuse into the particles readily and can thenbe polymerized in close association with the triacetate. When theprecipitate is dried, a compatible mixture of vinyl resin and triacetateis obtained.

When the vinyl monomers are such that they will form acetone solublevinyl polymers, and these vinyl monomers are used to modify cellulosetriacetate according to my invention, and at least 15% of the materialbased on the total Weight of modified cellulose triacetate is the vinylpolymer, the modified cellulose triacetate is acetone soluble. Thiseffect may also be obtained by mixing the cellulose triacetate in aceticacid, then adding to it an acetone soluble vinyl polymer so that theresulting mixture contains at least 15 of the vinyl polymer. Aparticularly unexpected advantage of obtaining acetone soluble modifiedcellulose triacetate is in the crystallinity of the films cast fromacetone solutions. Formerly crystallinity of cellulose triacetate wasobtained by subjecting the cellulose triacetate to temperatures of 200C. or higher. This feature is unexpected inasmuch as only a slightdegree of crystallinity is obtained when these modified cellulosetriacetate films are cast from methylene chloride-methanol solutions.

It will be understood, of course, that all of these m0dified cellulosetriacetate blends are also soluble in the normal cellulose triacetatesolvents, such as a methylene chloride-methanol mixture containing atleast 5 0% methylene chloride; and they may be extruded or cast intofilms, fibers, coatings and the like from these solvents. A particularlyvaluable use of the campatible blends is the production of shapedarticles by melt extrusion through spinnerets or other types oforifices. In such cases it is often desirable to incorporate from 15% to30% of a solvent or swelling agent such as triethylene glycol, butylacetate, etc., to the lower the extrusion temperature.

A wide variety of vinyl polymers may be employed in the process of thisinvention, including homopolymers and copolymers. Suitable polymers areobtained by employing monoethylenically unsaturated polymerizablecompounds containing a C=C group or more specifically a CH =C group.

Examples of suitable monomers include maleamides, and maleamates.Fumaric acid derivatives may also be used. Itaconic and citraconicesters, amides, and ester amides can be used as well as vinyl ethers,vinyl esters and vinyl ketones. The vinyl derivatives of benzene areoperative as represented by styrene, para methyl styrene and alphaacetoxystyrene. Unsaturated acids such as acrylic, methacrylic, maleic,fumaric, itaconic, citraconic, and their esters can be used as well asother monomers including methacrylonitrile, acrylonitrile, isopropenylacetate, N-vinyl irnides, N-vinyl lactams, fluorinated compounds,vinylpyridines, vinyl sulfones, vinyl chloride, vinylidine chloride andvinylidine cyanide.

Amides of acrylic and methacrylic acids are of particular value whenused in the form of homopolymers or copolymers. Several examples includethose represented by the general formula as follows:

R (H) /R' CH =J7O-N R is H or methyl. R is H, alkyl containing 1-4carbon atoms, phenyl, beta-hydroxyethyl, or beta-hydroxypropyl. R" is H,alkyl containing 1-4 carbon atoms, phenyl, beta-hydroxyethyl, orbeta-hydroxypropyl. R and R may be combined to form a cyclic structuresuch as is found in morpholine, piperidine and pyrrolidine. The acrylicand methacrylic amides of hydrazine and hydrazine derivatives are alsooperative. The composition of the vinyl resin is selected so that apolymer of the vinyl resin would be soluble in the solvent intended forprocessing cellulose triacetate such as, for instance, acetone, esters,higher ketones and the like.

In the event that the polymer is prepared prior to mixing with cellulosetriacetate, it may be prepared by the standard emulsion, bead, or bulkprocesses, using the commonly known catalysts. The polymer may then bemixed with the cellulose triacetate in acetic acid solution or by othermeans described below.

In a preferred embodiment of the invention in preparing -a mixture ofthe vinyl polymer and cellulose triacetate, the vinyl resin is preparedin acetic acid and the resulting solution is mixed with an acetic acidsolution of cellulose triacetate. In some cases it may be desirable toprepare the vinyl resin in an acetic acid solution of the cellulosetriacetate. Whether the modified cellulose triacetate is prepared by amixture of the polymer and the triacetate or whether the vinyl polymeris actually polymerized in the dissolved cellulose triacetate or swollenor gelled cellulose triacetate, the modified cellulose triacetate can beprepared so that it will be soluble in acetone or in some otherpreferred solvent.

From 60% to 85% cellulose triacetate may be present along with 40% to ofthe acetone soluble vinyl polymer based on the total solvents content.Other mutual solvents which may be used for cellulose triacetate and avinyl resin include dimethyl formamide, dimethyl acetamide, gammabutyrolactone, methylene chloride, 80 methylene chloridemethanol and thelike.

Suitable precipitants for obtaining the modified cellulose triacetateinclude water, benzene, lower alcohols, and the like when used withacetic acid. Other precipitants would be easily selected by one familiarwith the art.

Pigments such as carbon black, titanium dioxide, ironoxide,phthalocyanine dyes and the like may be added to the solutions.Plasticizers, fire-proofing agents, etc., can also be added. Agents toimprove the dyeing properties can be added as represented by polyN-isopropylacrylamide, poly dimethylacrylamide, polyvinylpyridine, etc.

In some cases, it is advantageous to incorporate in the blend a smallamount of high-boiling swelling agent orsolvent for the vinyl polymer.In order to improve-the solubility of the blend in acetone, esters, andthe like,

4; suitable additives include diethylene glycol, triethylene glycol,ethoxyethoxyethanol, and butoxyethoxyethanol.

The following examples are intended to illustrate my invention but notintended to limit it in any way:

Example 1 Five grams cellulose triacetate (43.5% acetyl) was disi solvedin a mixture of cc. acetic acid and 20 cc. water. Then 3 grams ofN-isopropylacrylamide, 2 grams of acrylonitrile, 0.1 gram potassiumper-sulfate, and 0.1 gram sodium bisulfite were added to the solutionand the mix- I The resultture was stirred at 50/ 60 C. for 18 hours. ingdope was poured into water to precipitate the cellulose triacetate andthe N-isopropylacrylamide copolymer as an intimate mixture. After theprecipitate had been washed free of acetic acid, it was stirred with asolution of 0.75 gram diethylene glycol and 25 cc. of water, then driedat 50-60 C.

The product gave a smooth, gel-free dope in acetone at a concentrationof 20-25% solids. Fibers were spun from the dope by the dry-spinningprocess. They dyed well with acid wool dyes, direct cotton dyes andcellulose acetate dyes.

Example 2 Fibers were spun from the acetone solution by the dryspinningprocess. The fibers were drafted ZOO-400% in a hot air chamber. Theydyed well with cellulose acetate dyes, acid wool dyes, and premetallizeddyes. Fibers had a hot bar sticking temperature of 230 C. which is about30 C. higher than the sticking temperature of fibers made fromacetone-soluble cellulose acetate.

Example 3 Five grams of cellulose triacetate (43.6% acetyl) weredissolved in a mixture of '80 cc. acetic acid and 20 cc. of water. Threegrams of methyl acrylate, -2 grams of acrylonitrile, 0.1 gram potassiumpersulfate, and 011 gram sodium bisulfitewere added. The mixture wasstirred at 50-60 C. for 18 hours. The dope was then poured into water toprecipitate the cellulose triacetate and the methyl acrylate copolymeras an intimate mixture.

The product was dissolved in acetone to give a smooth, stable dopehaving a dissolved solid content of 24%. Clear, tough films were castfrom the acetone solution; The films were useful as photographic filmbase. They had a crystalline structure as shown by X-ray.

Example 4 A solution of 60 grams vinyl acetate, 40 grams methyl acrylateand 2 grams of benzoyl peroxide in 300 grams of acetic acid was heatedat -100 C. for 12 hours to produce a clear, viscous dope or solution ofcopolymer. The solution was mixed with a solution of 300 grams ofcellulose triacetate and 3000 cc. of acetic acid and the mixture waspoured into water. The precipitatewas washed and dried.

The product gave a smooth, stable dope in acetone with a solids contentof 22-25%. Films cast from the acetone solution were useful asphotographic film base. The blend was also soluble in ethyl acetate.

Films cast from the acetone solution of the blend showed a high degreeof crystallinity when examined by X-ray. The hot bar stickingtemperature of the film was 250-260 C.

[Fibers were spun by extruding the acetone solution into a hot airchamber. The fibers showed only a slight degree of crystallinity. Afterdrafting -200-300% in a hot air chamber, the fiber showed a high degreeof orientation 5. and crystallinity. It had a hot barsticking-temperature of 230240 C.

Example 5 A solution of 1 grams of methoxyethyl methacrylate and 1. 5grams benzoyl peroxide in 300 cc. of acetic acid was heated at 90100 C.for 8 hours. The viscous solution was mixed with a solution of 200 gramscellulose triacetate (43.5% acetyl) in 3000 grams of acetic acid. Theblend of cellulose triacetate and methacrylic ester resin wasprecipitated by pouring the acetic acid solution into water. Theprecipitate was washed and dried.

The blend was soluble in acetone and gave clear films when the solventwas evaporated. Solutions of the blend in ethylacetate were useful formaking protective coatings.

Example 6 A solution of 100 grams methyl acrylate and 1.0 gram benzoylperoxide in 300 grams of acetic acid was heated at 5060 C. for 24 hours.The viscous solution was mixed with a solution of 400 grams cellulosetriacetate (43.2% acetyl) in 4000 grams of acetic acid. The blend ofcellulose triacetate and polymethyl acrylate was precipitated by pouringinto water. The precipitate was washed and dried.

The blend was dissolved in acetone at about 15 C. to give a clear,smooth dope. The dope was stable at room temperature for several days.Films cast from the dope were clear and showed a high degree ofcrystallinity when examined by X-ray. The strength of the film wasincreased by drafting l50300% at an elevated temperature.

Fibers were spun by extruding the acetone dope into a hot air chamber.After the fibers had been drafted at an elevated temperature, followedby heat treatment at 200-250 C., they gave a crystalline X-ray pattern.

'Films cast from a solution in 90 methylene chloridemethanol werenon-crystalline. However, they developed a crystalline pattern whenheated for a few minutes at 200-240 C. Fibers spun from a solution inmethylene chloride-methanol were non-crystalline but they developed acrystalline pattern when drafted and heat treated.

Example 7 Forty grams of methyl acrylate, 60 grams,N,N-diethylacrylamide, 2 grams benzoyl peroxide, and 400 grams cellulosetriacetate were dissolved in 4000 grams of acetic acid and the mixturewas stirred at GO-70C. for 24 hours. The resulting solution was pouredinto water to precipitate an intimate mixture of cellulose triacetateand the copolymer.

The blend was soluble in acetone. Fibers spun from the acetone solutionwere drafted and heat-set. They dyed readily with cellulose acetatedyes, acid wool dyes, and direct cotton dyes.

Example 8 A solution containing 14 milliliters of 10% gelatin, 1milliliter of 7.5% saponin, and 10 milliliters of water is added to 5milliliters of medium speed silver bromoiodide emulsion and the mixtureis coated to a wet thickness of 0.006-inch on a sub-modified cellulosetriacetate support, cast from the composition described in Example 7 anddried. The coating is then exposed under an image and developed in aN-methyl-p-aminophenol (or 1Metol)-hydroquinone developing composition-to form a negative silver image. The residual silver halide is removedwith hypo, leaving a permanent negative silver image. Color emulsionscontaining incorporated couplers may also be coated on this support andprocessed to yield dye images.

Example 9 Cellulose triacetate (43.5% acetyl) was prepared in a twoacetic acid-one acetic anhydride solution by the usual method employingsulfuric acid as a catalyst. The ester was precipitated as fine gelparticles by the addition of water. The precipitate was washed free ofacetic acid and was then suspended in water to give a ratio of 20 g.cellulose triacetate [on a dry basis] to 130 g. water. The followingmaterials were added to the suspension: 1.5 g. sulfonated mineral oil,30 g. methyl acrylate, and 0.3 g. potassium persulfate. The mixture wasstirred at 50'- '60 C. for 24 hours. The product, after filtering anddrying, weighed 48 g. and consisted of an intimate blend of cellulosetriacetate and polymethyl acrylate in approximately a 40- 60 ratio.

The blend gave a clear, stable dope in 90 methylene chloride-10 methanoland clear, flexible, strong films were obtained by casting on glassplates.

One part of the blend and 2 parts cellulose triacetate were dissolved in15 parts 90 methylene chloride-10 methanol to give a smooth, stabledope. Fibers were spun by the dry-spinning method and drafted 50% at anelevated temperature. The fibers, which contained approximately 20%polymethyl acrylate, dyed heavily with cellulose acetate dyes at theboil. They had a hot bar sticking temperature of 24025 0 C.

This com-position (-20) is also useful as a photographic film base. Thepolymethyl acrylate imparts flexibility.

Example 10 Thirty grams N-isopropylacrylamide, 20 g. methyl acrylate,and 1.0 g. benzoyl peroxide were added to a solution of 200 g. cellulosetriacetate 43.7% acetyl in 1500 cc. of acetic acid. The solution wasstirred at 60- 70 C. for 24 hours. The blend of cellulose triacetate andvinyl resin was precipitated by pouring the acetic acid solution intowater. After washing and drying, the product gave a smooth, stable dopein methylene chloride-10 methanol. Fibers spun from the dope dyed wellwith cellulose acetate dyes, acid wool dyes, and premetallized dyes.Example 11 A solution containing 75 parts cellulose triacetate, 15 partsdimethytlacrylamide, 10 parts N-tert butylacrylamide, 0.5 pant potassiumpersulfate, 850 parts acetic acid, and 150 parts water was stirred at6070 C. for 24 hours. The .blend of cellulose triacetate and vinylpolymer was precipitated by pouring the acetic acid solution into water.The blend was ground to a particle size of mesh and 75 parts was mixedwith 25 parts of tniethylene glycol. The mixture was extruded through aspinneret at 200- 220 C. After the glycol was washed out, the fibersdyed well with cellulose acetate dyes, acid wool dyes, and premetallizeddyes.

Example 12 Eighty parts of cellulose triacetate, v20 parts of N,N-dibutylacrylamide, 1 part of benzoyl peroxide, 200 parts of acetic acid,and 200 parts of water were stirred at 50-60 C. for 24 hours. Thecellulose triacetate did not dissolve, but swelled appreciably so thatthe N,N-dibutylacrylamide difiused into the particles and polymerized.The product was isolated by pouring into water. Fibers spun from theblend dyed well with cellulose acetate dyes, acid wool dyes, andpremetallized dyes.

Example 13 One part of cellulose triacetate, one part ofN,-N-diethylacrylainide, 0.02 part acetyl peroxide, 9 par-ts methylenechloride, and 1 part methyl alcohol were mixed until a clear solutionwas obtained. The solution was then heated at 50 C. for 24 hours. Thesolution containing triacetate and vinyl polymer was mixed with asolution of 4 parts cellulose triacetate dissolved in 14.4 partsmethylene chloride and 1.6 parts methyl alcohol. Fibers spun from theresulting mixture dyed well with cellulose acetate dyes, acid wool dyes,and premetallized dyes.

Cellulose triacetate differs considerably from cellulose esters asusually intended by the use of that term. For instance, cellulosetriacetate is insoluble in acetone and has a melting point about 40 C.higher than the material normally called cellulose acetate. Moreover,cellulose triacetate. can be crystallized while cellulose acetate isusually considered to be in an amorphous state. The fundamentaldifference between triacetate and other celluzlose esters is discussedby Malm, et al., Industrial and Engineering Chemistry, 43 684 (1951);and also in An Introduction to the Chemistry of Cellulose by Marsh andWood, page 201.

Cellulose triacetate is known to be very incompatible with practicallyall types of vinyl polymers, and solutions or dopes containing the twomaterials separate into two layers on standing. This is especially truewhen the usual spinning or coating solvent 90% methylene chloride-10%methanol is used. In contrast to this, my process makes it possible toobtain clear, stable dopes that contain cellulose triacetate incombination with a variety of vinyl polymers.

As used therein the term cellulose triacetate refers to a celluloseester containing more than 43% acetyl. Such an ester is highly insolublein acetone and melts in the range of 275-300 C. as compared with 240-250for the acetone soluble type. Cellulose triacetate develops a highlycrystalline structure when subjected to suitable heat treatment.

The compositions to be operative in my invention may contain 20-95%cellulose triacetate to have improved properties. In the event that anamount of modifier less than 5% is used, the beneficial effect such asplasticizing, dyeing and the like are not obtained. In. the event thatan amount of modifier greater than 80% is used, the resulting materialhas poor physical properties such as tenacity, extensibility, andresistance to temperature change.

Fibers spun from solutions containing this modified cellulose triacetatecan be dyed to heavy shades with cellulose acetate dyes, acid wool dyes,direct cotton dyes, and premetallized dyes. Standard procedures can beused since it is not necessary to dye at pressures above atmospheric.Swelling agents or dying assistants are not required.

Proportions designated herein are by weight otherwise indicated.

I claim:

1. A process for forming a blend of a cellulose triacetate andpolymethyl acrylate which comprises the steps of (a) blending togetheringredients consisting essentially of: (1) 40 weight percent of acellulose triacetate having more than 43% acetyl content and (2) 60weight percent of methyl acrylate, said blending being performed in thepresence of a liquid selected unless from the group consisting of aceticacid, methylene chloride, methylene chloride-methanol solution,dimethyl-sulfolane, ethylene chlorohydrin, and water; and

(b) polymerizing said methyl acrylate in the presence of said cellulosetriacetate to form said blend.

2. A process for forming a blend of a cellulose, triace tate andpolymethyl acrylate which comprises the steps, of

(a) blending together ingredients consisting essentially of: (1) 40weight percent of a cellulose triacetate having more than 43% acetylcontent and (2) 60 Weight percent of methyl acrylate, said blendingbeing performed in the presence of acetic acid;

(b) polymerizing said methyl acrylate in the presence of said cellulosetriacetate to form said blend; and (c) separating said blend of acellulose triacetate and polymethyl acrylate from said acetic acid.

3. A process for forming a blend of a cellulose triacetate andpolymethyl acrylate which comprises, the steps of (a) blending togetheringredients consisting essentially of: (1) 40 weight percent of acellulose triacetate having more than 43% acetyl content and (2) 60weight percent of methyl acrylate, said blending being performed in thepresence of water; (b) polymerizing said methyl acrylate in the presenceof said cellulose triacetate to form said blend; and

(c) separating said blend of a cellulose triacetate and polymethylacrylate from said water.

References Cited by the Examiner OTHER REFERENCES Ott et al.: Cellulose,Part H, High Polymers, vol. V, 2nd edition, published by IntersciencePublishers, New

5. York, 1954, pages 794 and 795.

JOSEPH L. SCHOFER, Primary Examiner.

NORMAN G. TORCHlN, JAMES A. SEIDLECK,

Examiners.

J. T. BROWN, Assistant Examiner.

1. A PROCESS FOR FORMING A BLEND OF A CELLULOSE TRIACETATE ANDPOLYMETHYL ACRYLATE WHICH COMPRISES THE STEPS OF (A) BLENDING TOGETHERINGREDIENTS CONSISTING ESSENTIALLY OF: (1) 40 WEIGHT PERCENT OF ACELLULOSE TRIACETATE HAVING MORE THAN 43% ACETYL CONTENT AND (2) 60WEIGHT PERCENT OF METHYL ACRYLATE, SAID BLENDING BEING PERFORMED IN THEPRESENCE OF A LIQUID SELECTED FROM THE GROUP CONSISTING OF ACETIC ACID,METHYLENE CHLORIDE, METHYLENE CHLORIDE-METHANOL SOLUTION,DIMETHYL-SULFOLANE, ETHYLENE CHLOROHYDRIN, AND WATER; AND (B)POLYMERIZING SAID METHYL ACRYLATE IN THE PRESENCE OF SAID CELLULOSETRIACETATE TO FORM SAID BEND.